Portal:Trees
The Trees Portal
In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are usable as lumber or plants above a specified height. In wider definitions, the taller palms, tree ferns, bananas, and bamboos are also trees.
Trees are not a monophyletic taxonomic group but consist of a wide variety of plant species that have independently evolved a trunk and branches as a way to tower above other plants to compete for sunlight. The majority of tree species are angiosperms or hardwoods; of the rest, many are gymnosperms or softwoods. Trees tend to be long-lived, some reaching several thousand years old. Trees have been in existence for 370 million years. It is estimated that there are around three trillion mature trees in the world.
A tree typically has many secondary branches supported clear of the ground by the trunk, which typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another. For most trees it is surrounded by a layer of bark which serves as a protective barrier. Below the ground, the roots branch and spread out widely; they serve to anchor the tree and extract moisture and nutrients from the soil. Above ground, the branches divide into smaller branches and shoots. The shoots typically bear leaves, which capture light energy and convert it into sugars by photosynthesis, providing the food for the tree's growth and development.
Trees usually reproduce using seeds. Flowers and fruit may be present, but some trees, such as conifers, instead have pollen cones and seed cones. Palms, bananas, and bamboos also produce seeds, but tree ferns produce spores instead.
Trees play a significant role in reducing erosion and moderating the climate. They remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues. Trees and forests provide a habitat for many species of animals and plants. Tropical rainforests are among the most biodiverse habitats in the world. Trees provide shade and shelter, timber for construction, fuel for cooking and heating, and fruit for food as well as having many other uses. In much of the world, forests are shrinking as trees are cleared to increase the amount of land available for agriculture. Because of their longevity and usefulness, trees have always been revered, with sacred groves in various cultures, and they play a role in many of the world's mythologies. (Full article...)
Kauri gum is resin from kauri trees (Agathis australis), which historically had several important industrial uses. It can also be used to make crafts such as jewellery. Kauri forests once covered much of the North Island of New Zealand, before early settlers caused the forests to retreat, causing several areas to revert to weeds, scrubs, and swamps. Even afterwards, ancient kauri fields and the remaining forests continued to provide a source for the gum. Between 1820 and 1900, over 90% of Kauri forests were logged or burnt by Europeans.
Kauri gum forms when resin from kauri trees leaks out through fractures or cracks in the bark, hardening upon exposure to air. Lumps commonly fall to the ground and can be covered with soil and forest litter, eventually fossilising. Other lumps form as branches forked or trees are damaged, releasing the resin. (Full article...)Did you know? -
- ... that veneration of the Amla tree (pictured), in particular on Amalaka Ekadashi, is due to the belief that the god Vishnu resides in and near the tree?
- ... that the future of the tropical tree Milicia regia for timber production is threatened by a gall fly, Phytolyma lata?
- ... that the churchyard of All Saints Church, Ulcombe in England contains a yew tree claimed to be more than 2,000 years old?
- ... that seeds of the extinct tree Eucommia eocenica have been found with latex covered fossils?
- ... that the fruits of the Lecythis ampla tree resemble little wooden pots with lids?
- ... that fossilized seeds of the extinct tree Eucommia montana are found from British Columbia to Colorado?
- ... that the Australian tree Agathis atropurpurea is known as the black kauri or the blue kauri because of the colour of its bark?
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The stone pine, botanical name Pinus pinea, also known as the Italian stone pine, Mediterranean stone pine, umbrella pine and parasol pine, is a tree from the pine family (Pinaceae). The tree is native to the Mediterranean region, occurring in Southern Europe and the Levant. The species was introduced into North Africa millennia ago, and is also naturalized in the Canary Islands, South Africa and New South Wales.
Stone pines have been used and cultivated for their edible pine nuts since prehistoric times. They are widespread in horticultural cultivation as ornamental trees, planted in gardens and parks around the world. This plant has gained the Royal Horticultural Society's Award of Garden Merit. (Full article...)General images
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